+#ifdef USB_6KRO_ENABLE
+ int8_t i = cb_head;
+ int8_t empty = -1;
+ if (cb_count) {
+ do {
+ if (keyboard_report->keys[i] == code) {
+ return;
+ }
+ if (empty == -1 && keyboard_report->keys[i] == 0) {
+ empty = i;
+ }
+ i = RO_INC(i);
+ } while (i != cb_tail);
+ if (i == cb_tail) {
+ if (cb_tail == cb_head) {
+ // buffer is full
+ if (empty == -1) {
+ // pop head when has no empty space
+ cb_head = RO_INC(cb_head);
+ cb_count--;
+ }
+ else {
+ // left shift when has empty space
+ uint8_t offset = 1;
+ i = RO_INC(empty);
+ do {
+ if (keyboard_report->keys[i] != 0) {
+ keyboard_report->keys[empty] = keyboard_report->keys[i];
+ keyboard_report->keys[i] = 0;
+ empty = RO_INC(empty);
+ }
+ else {
+ offset++;
+ }
+ i = RO_INC(i);
+ } while (i != cb_tail);
+ cb_tail = RO_SUB(cb_tail, offset);
+ }
+ }
+ }
+ }
+ // add to tail
+ keyboard_report->keys[cb_tail] = code;
+ cb_tail = RO_INC(cb_tail);
+ cb_count++;
+#else